Screw-cutting attachment



(No ModeL) J. HARTNESS. SCREW CUTTING ATTACHMENT.

Patented Jan. 4, 1898.

QN C

MTNESEEIS "by my present invention.

UNITED STATES A PATENT rrrcn JAMES HARTNESS, OF SPRINGFIELD VERMONT.

scREw-CUTVTlNG ATTACHMENT.

SPECIFICATION forming part of Letters Patent No. 596,750, dated January4, 1898.

Application and May 1s, is 97.

To @ZZ wiwi/)tit may concern,.-

Beit known that I, JAMES Hanrunss, vof Springfield, in the county of'Vindsor and State of Vermont, have invented certain new and usefulImprovements in Screw-Cutting Attachments,of which the following is aspecification.

This invention relates to screw-cutting attachments for turretulathesand other machimes, and it relates more particularly to a method ofmounting screw-cutting dies in tandem, so as to cut simultaneously twoor more threads at diderent points in the length of a rod or bar.

In certain classes of screw-cutting work, such as in the manufacture ofstay-bolts for steam-boilers, where these belts are threaded at bothends .to engage parts vsuch as the outer and inner shells surroundingthefirebcx, it is essential to the best results that a certain fixedrelation should exist between the shell-engaging threads on each boltand also thata corresponding fixed relation should exist between. theboiler-threads which the bolts engage. With present methods itfrequently happens that these relations are variable, and in consequenceone stay-bolt in a boiler may be forcing the shells apart while the nextadjoining bolt is drawing them together. Detrimental strains are thusproduced, which may be avoided by the improved method of cutting threadswhich is'furnished The object of my invention may be said to be theproduction of devices for simultaneously screw-threading a rod or bar attwo or more places in its length andgfcr obtaining a determinaterelation between the threads at the different places.`

Theinvention consists in the novel features of construction and relativearrangement of parts, which I shall now proceed to describe and claim,reference being had to the accompanying drawings, in which- Figure lrepresents in vertical longitudinal section and side elevation twoscrew-cutting dies arranged in tandem according to my invention, thework being shown in position. Fig. 2 represents a front elevation of thesame. Fig.. 3 represents a side elevation of Serial No. 637,045. (Nomodel.)

the work, which in this case is a boiler staybolt.

The same letters of reference indicate the same parts in all thefigures.

For the sake of illustration merely I have shown two dies similar to thescrew-cutting die described in Letters Patent No. 565,746, granted to meAugust l1, 1896, although my present invention is not limited to the useof dies of this pattern. A brief description of these dies willtherefore sufiice.

The letter a designates the shank or rear member of the die-body in eachof the dies A A', and c designates the forward member, which is movableslightly in a direction longitudinal with the shank a, but is rigidlyengaged laterally and concentrically therewith.

In diverging slots in the face of the member c are located the cuttersor chasers e, which are engaged by a four-part cam f and are adapted tobe moved thereby outwardly or inwardly to open or close thevdie. The camis embraced by a sleeve or cam-holder f', which is iitted to rotate 0nthe member c of the die-body, being adjustably connected with the cam bymeans of a screw f2. The said cam-holder and cam may be partiallyrotated to open and close the die by means of a handle Iw' on thecam-holder, and the two are adapted to be held in rigid engagement withthe member c by a spring-pressed bolt "w, located in the handle 'w' andfitted to enter a shallow recess on the periphery of the said member c.

Y To automatically open the die, devices are provided as follows: A ringor collar g is connected with the cam-hclder by means of knurlheadedscrews a: a: and extends back over the shank a, a suitable spring beingintroduced between the collar and said shank whose tension throws thecam to a die-opening position when the bolt w becomes disengaged fromthe member c. This disengagement is effected when the member c movesoutward relatively to the shank a by means of a sliding block m, whichoccupies an aperture in the member c and is provided with a headoccupying a slot in the shank a and engaging said shank, so as to remaintherewith when the member c moves outwardly. When said movement IOOoccurs relatively to the shank a, the bolt w is raised and disengaged bymeans of a tappet-piece or releasing-pin n, whose lower end occupies agroove in the block, said groove having a curved or inclined base whichacts to thrust the tappet-rod upwardly against the bolt. This automaticdie-opening action takes place when the forward movement of the shank ahas ceased, and the cutters and by the continued rotation of the work.

The joint occurring where the members d and c abut is closed to excludedirt and chips` by a fiat resilient band d, sprung into a recess in thewall of the central opening of the chuck or die-body.

In carrying out my invention, as hereinbefore stated, I contemplate theemployment of two or more screw-cutting dies, such as A and A', mountedtandem or one behind the other, as shown in Fig. l, for the purpose ofacting simultaneously on two different portions of a rod or bar, such as7c, and I will n'ow proceed to describe a method of mounting the dies.

The shank d of the forward die A is formed with a downwardly-extendingattaching-plate a and is provided with attaching-bolts 7L h, by means ofwhich it is secured at the forward end of a base-plate or support z'.The shank al of the rear die A is extended rearwardly and held in asplit collar j', forming part of a holder j, which is adjustably securedto the base-plate t' by means of attaching-bolts o, the said boltsoccupying slots o in the holder and screwing into threaded sockets o2 inthe base-plate.

The die A is held in longitudinal alinement with the forward die A bymeans of a tenon j, formed on the under side of the holder j and fittingin an elongated groove z" on the upper surface of the base-plate t'. Thesaid base-plate is formed with a similar tenon i2, which is adapted toengage a groove on the top of a lathe-turret or equivalent support onanother machine, to which the base-plate is affixed, and by said tenonthe dies are held in longitudinal alinement with the work.

The slot o (indicated by dotted lines in Fig. l) is made longer than thewidth of the shank of the bolt o, so as to allow a small amount oflongitudinal adjustment of the die A with respect to the die A, and amore liberal adjustment corresponding to the different lengths ofstay-bolts required is provided for by a series of threaded sockets oBo4 o5 similar to the socket o2 and placed at suitable distance apart,the bolt o being shifted to such a socket as will give the desireddistance between the cutters c of the two dies A and A.

It is obvious that the construction might be reversed by having the reardie A permanen-tly fixed and the forward die A adj ustably mounted.

In Fig. l a cylindrical bar 7c is shown as being operated uponsimultaneously by the dies to form screw-threads at the ends of thestaybolt, and in Fig. 3 the finished stay-bolt K is shown. It will benoticed that the bolt. is reduced to form a waist between the twothreaded portions. The common method is to form the bolt of uniformdiameter and screw-thread it from end to end, but I prefer theconstruction shown as facilitating the threading operation and theplacing of the bolts in position in the boilers. the member c continueto be moved forward One of the obstacles to exactness in making andfitting stay-bolts in boilers finds its cause in a permanent shrinkageor elongation which e takes place during the process of hardening 5 thetaps which are used to produce a screwthread in the holes in theboiler-shells.

It is practically impossible by the present used methods to thread astay-bolt in such a manner as to correspond exactly to the lead of a tapafter it has thus changed from its correct lead. By the use of thetandem-die holderl the dies may be located relative to each other byplacing the tap which is used to produce the thread in the boilers intothe dies by sliding the movable die the correct distance from the fixeddie, so that the tap will enter both. This locates the dies in thecorrect relative position, and the dies in turn will producescrew-threads on the stay-bolt which will correspond to the lead of thestay-bolt tap. If the thread of such a bolt is found to be longer'orshorter than that of the tap, a slight additional adjustment of the diereadily corrects it. The taps may be produced in any desired manner ormay be cut directly struction may be altered or modified to an extentconsistent with the scope of my invention.

1. As a means for threading a piece of work simultaneously in the samedirection at separate portions of its length, a screw-cutting devicecomprising two or more screw-cutting dies mounted with their axes inlongitudinal alinement, and adjustable means for maintaining said diesat a lixed distance apart.

2. A screw-cutting device comprising a suitable base, and two or morescrew-cutting dies rigidly mounted thereon with their axes inlongitudinal alinement, the said dies being capable of relativelongitudinal adjustment.

3. A screw-cutting attachment comprising a suitable base, and two ormore screw-cutting dies rigidly mounted thereon, with their axes inlongitudinal alinement, one of said dies being fixed, and the otherbeing adjustable relatively to the fixed die.L g

4. A screw-cutting device comprising a supzog port or base-plate, ascrew-cutting die fxedly mounted thereon, a holder having a tenon fittedto engage e longitudinal groove in the hase-plate, means for securingseid holder to the base-plate in successive positions relatively to thefixed die, and a screw-cutting die mounted in said holder, with itscentral axis in longitudinal alinement with the oentral axis ofthe fixeddie.

In testimony whereof I have signed my 1o name to this specification, inthe presence of two subscribing Witnesses, this 13th day of May, A. D.1897.

JAMES HARTN'ESS.

Witnesses:

D. S. BROWNELL, J. W. BENNETT.

